Given all that has come before it, the report published this week by Human Rights Watch (HRW) detailing British complicity in the torture of terror suspects will hardly come as a surprise. The findings corroborate the Guardian's own investigations, as well as a series of embarrassing disclosures that the government has been forced into making by the courts. The battle over the "secrets" that the US and British regimes are still refusing to divulge has descended into a farce, with lawyers using CIA-directed ellipses when they write about the abuse meted out to their clients, all of which allow us to read, quite clearly, between the lines. Our government has facilitated torture across the world.

With all the hand-wringing about the legal, political, and moral implications of this, one salient point often gets sidelined. Yet it's perhaps the most pressing one of all. Torture doesn't work. In fact, it often directly compromises intelligence-gathering.

As the HRW report underlines, British collusion in prisoner abuse in Pakistan has actually interfered with attempts to prosecute suspects in the British courts. It quotes a British intelligence source as saying that the violent treatment of one of the alleged masterminds of the 2006 airline plot, Rashid Rauf, had been a "disaster" that made any "successful prosecution in Britain most unlikely".

Add to this the fact that the fatal WMD myth gained currency thanks to so-called "intelligence" now known to have been gleaned through forced confession, plus the legal headache that the 9/11 suspects soon to be tried in New York will present – 183 instances of waterboarding are likely to make much of the evidence against the key defendant, Khalid Sheikh Mohammed, inadmissible – and it's plain that we are looking at the whole issue back to front. No matter the innocence or guilt of the parties involved; no matter what your views on the ethics of psychological and physical torment; whether or not you think there are some extreme cases where it's warranted to prevent a greater evil; torture is astonishingly ineffective.

Former Guantánamo detainee Binyam Mohamed has admitted that the abuse he endured in secret rendition locations and, finally, in Cuba, made him ready to confess to anything, implicating people he'd never heard of and making up lies just to second-guess his captors in the hope of avoiding worse. It's easy to imagine that anyone who went through what he did – mutilation, mind games, sleep deprivation and beatings that left him unconscious – would do the same. How, in the condition he was reduced to, could any "intelligence" possibly be extracted from him?

Another former Guantánamo inmate, Omar Deghayes, confirmed this. "If you thought you could say something to stop the torture, you'd say anything. Then they'd stop torturing you, try and get you to sign a confession, and you'd realise what you were doing, and you'd refuse. And then it would begin all over again."

Deghayes was initially detained in Bagram, Afghanistan. Meanwhile his wife and child were being held in neighbouring Pakistan and this, understandably, made him even more ready to spout whatever was wanted of him. But over time the process had the reverse effect. "Even if you'd somehow managed to come across some real information, something that might be useful to them, after everything they had done to you, you'd never help them. Never," he told me.

Clive Stafford Smith, who has represented many Britons tortured in the past eight years, argues that Britain and America's response to 9/11 has created a much larger group of extremists than existed before the attacks:

We've taken the reservoir of goodwill that existed for Americans after what happened in New York and turned it into hatred. Politicians and the media spend their whole time obsessing about the next hypothetical crime – plane into a building, bomb in a shoe and so on – so they will do anything they can try and stop it. This means they're hypocritical about human rights, they detain people, put them in Belmarsh or Guantánamo, and what they end up doing is actually making the world far more dangerous.

Stafford Smith would be the last to portray David Miliband and his minions as evil caricatures who sit around plotting torture in far-flung lands just for the sake of it. But what happened to Mohamed, Deghayes and thousands of others are not isolated or historical incidents. British and American leaders have yet to grasp that the methods their agents and allies use don't work – and so, in Afghanistan and elsewhere, it's still business as usual. One of Deghayes's relatives is now detained in Bagram; the last time his wife saw him his hands and feet were bound in plaster. Bagram, Omar tells me, makes Guantánamo "feel like a holiday camp".